The present invention relates, in general, to a method and apparatus for controlling the shift action during up-shift in an automatic transmission and, more particularly, to a method of appropriately controlling such a shift action by a transmission control unit integrated with an engine control unit.
In the operation of vehicle automatic transmissions, a transmission control unit controls a plurality of solenoid valves to control the flow of transmission oil in accordance with the running speed of a vehicle, the throttle valve position and the other sensed operational conditions of the vehicle. This allows the gears of a desired transmission mode to automatically engage to transmit power. When a driver operates the shift lever of an automatic transmission to a desired stage while driving, the hydraulic ports of a manual valve are selectively opened under the duty control of solenoid valves to selectively actuate the drive parts of a shift gear mechanism using transmission oil fed from an oil pump, thus accomplishing a desired transmission mode.
During the shift action to accomplish a desired transmission mode, some frictional parts of the automatic transmission are changed from an engaged state to a disengaged state. Other frictional parts are changed from a disengaged state to an engaged state. The timing of engagement or disengagement of the frictional parts determines the power transmission performance of such an automatic transmission. Therefore, methods for controlling such a shift action have been actively studied in order to improve the power transmission performance of automatic transmissions in recent years.
The conventional automatic transmission for vehicles is designed to be shifted between lower and higher gears through three shift modes: an up-shift mode wherein the transmission is sequentially shifted into a higher gear through first-to-fourth up-shift in accordance with the running speed of a vehicle, a down-shift mode wherein the transmission is sequentially shifted into a lower gear through fourth-to-first down-shift, and a down skip-shift mode wherein the transmission is shifted into a lower gear through fourth-to-second skip-shift and third-to-first skip-shift.
During a shift action in the up-shift mode of a conventional automatic transmission, the desired run-up and smooth shift action are accomplished by appropriately controlling transmission oil pressure and pre-fill time. In order to accomplish the desired smooth shift action when turbine blow-up is generated during an up-shift in the prior art, the shift action in the up-shift mode has been controlled such that the duty-controlled oil pressure in an initial shift cycle are learned and corrected to increase the oil pressure in a next shift cycle. As used herein, blow-up or turbine blowup refers to a condition wherein turbine rpm rises abnormally during the up-shift.
However, the conventional method of controlling the shift action in the up-shift in an automatic transmission does not perform learning of turbine blow-up in proportion to the blow-up value or amount. In addition, conventional methods control the shift action in such an up-shift only by the learning of turbine blow-up, so it is necessary to undesirably endure turbine blow-up overspeed until the blow-up learning value converges to a desired value.
The conventional shift action control method does not have techniques for determining tie-up of turbine rpm, so it is impossible to reduce the excessive learning value of turbine blow-up when the learning of turbine blow-up is excessively performed. Therefore, it is inevitable to endure tie-up impact and reduce durability of the automatic transmissions due to such tie-up impact.
The present invention provides a method and apparatus of controlling the shift action in an up-shift mode of a vehicle automatic transmission, which appropriately controls the shift action in such an up-shift mode by a transmission control unit integrated with an engine control unit, thus restricting turbine blow-up during the shift action, stabilizing the learning of turbine blow-up, reducing an excessive learning value of blow-up to an acceptable level, and thereby accomplishing desired smoothness of the shift action, in addition to improving durability of automatic transmissions.
According to a preferred embodiment of the present invention controlling the shift action in an up-shift mode comprises determining whether a turbine blow-up amount or value is higher than a predetermined reference value when a shift command is applied during operation of the vehicle; performing blow-up learning control in proportion to the turbine blow-up amount, and performing engine torque reduction control when the blow-up amount is higher than the reference value; determining whether turbine rpm tie-up is generated when it is determined that the turbine blow-up amount is not higher than the reference value; performing tie-up learning control when it is determined that turbine rpm tie-up is generated; and performing a normal control when it is determined that turbine rpm tie-up is not generated.